Electric discharge tube



' INVENTOR. I 1012mm; 01W M. VZ/V OVHZBEK A TT012NK A. J. W. M. VANOVERBEEK ELECTRIC DISCHARGE TUBE Flled Aprll 22, 1946 Jan. 9, 1951a.zpluralitymf secondary electrons.

Patented Jan. 9, 1951 onrrizo PATENT eerie-E V nilno'rmoiii sziiinoeronn Adrianne Johannes ilhehnus .Marie van iover- .heek, .Eindhoven;Netherlands, assignor, by ..mesne assignments, .to Harf'foriiiNationalBank an'd'Trust Company, Hartfordfflonn astrustee mppfication-Aprfl 222,1946,='Senial::l\lo.:; 663,822

the Netherlands February. 15,1943

LiSe'ctionifPublicLaw 690, llu'gust 8, 191% Patent expires February 15,1963 This :invention relates atcuan telectric .-.discharg tribe ahavingia. secondaryeemission lelectrode 1:.e.

anrelectrcde iwhichpwhen."beingstruckby mpritial .riifferen'cesbetweenzthe anode and 113116 .pre

ceding auxiliary cathode iusually :doesnot .rexcee'd 50 ivol ts .in:.-:order 'rthat the voltage TlGO :be .capplied to the 'itubesshouldcnotrbecome tooxhigh. Consequently, in order that the field'bBtWEBIlIFthE fian- Odfiitlld theaacxilaryicathode shall :haveaisulilcient value :the "distance :between them :must the small.

11; is aiready known to wdesi'gn the eauxilary cathode as arnettingof'rmeta'l sgauze son Ito which anaactivating'agentisra plied.inahisscaseiithe .an'odeiis located close rbhindthe met'ting. has thedrawback that :a slarge mart Of the tprimary electrons steadily (passesthrough fthe L-netting rand reaches-the anode withotitiihaving dislodgedany secondary electrons. Again it is known to place "itheiflattsedonflar-yeemission electrode .and .the flat .anode .at .aiairly largeangle with respect to one another. .-In .this event the auxiliarycathode lies in the path ofthe primary electrons and the anode islocated at the side. As az riile, however, the field "is not sufiicient'to prevent space charges.

;?In order zto .make the .field :rbe'tween the -.two electrodesu'stronger it is necessary aimakezthe :angle very small. This .has the:.drawback; however, that :in'zthe .case .of .the ianod'e voltage beinga little too high which may, for instance, occur in the event of feeblecontrol or for other reasons, a part of the primary electrons is movingdirectly to the anode without having dislodged secondary electrons fromthe auxiliary cathode. Owing to the high anode voltage the paths of theprimary electrons are curved to such a de gree that these electrons findtheir way to the anode instead of to the auxiliary cathode. Thisdetrimental effect also occurs when by providing stops which areapertures or useful openings of a lens, usualy adjustable by means of adiaphra'gm, .the beam :of primary :electrons at-.the

normal anode vol'tagersolely. reaches .the auxiliary cathode. .Narrowingof the steps would result in that at .the same "voltage the current:from the cathode to the auxiliary cathode becomes. much too Theinvention has .for itspurpose .to cure these drawbacks. To this end theanode of a secondary-emission .tube, in which the anode is .locatedoutside-the paths of the ,primary electrons, is ourved and faceswithlitsconvexiside the secondary-iemission electrodeinsuch azmannerthat the distance between the .anode and secondaryemission electrodedecreaseswitha-an increasetin distance. from the ,primary "cathode. Ofcourse, .thesdistance between them should :be :small and thestronge'st.:curvatur.e of the anode .lies .at least approximately :in the plane ofthe paths of the primary electrons. Consequently, the :anode is curvedin the same sense :as the paths of the primary :eleetrons, was a'.-resu1t of which these electrons, notwithstanding the increase inanode voltage, do not so easily .find their way :to the anode.

In a particularly: suitable form (of constructionthersecondary-remission electrode-is curv-ed. in .the samessense as-the-anode. In this case thesdistance .5 tion comprises rtwo .cathodesandtwo anodes but only .zoneisecondary-emission electrode whose acti=ve:parts rare curved towards the associated anodes. .The tube :isparticularly suitablez forzuse in so-called lpush-pull-arrangement,sincethe inlet of the 2auxiliarycathode does not carry a highfrequencyvoltage with respect to the cathode.

:In 'order that the inventionmay be cl arly understood 'and .:readilycarried into effect it will nowibe'describedrmoreffullywith reference tothe accompanying drawing, given by way of example.

Figure 1 is a cross-section of the electrode system of a discharge tubecomprising an auxiliary cathode which is placed at a small anglerelatively to the anode.

Figure 2 is a cross-section of the electrode system of a tube, in whichthe convex side of the anode faces the auxiliary cathode.

Figure 3 represents the electrode system of a tube having two cathodes,two anodes and one secondary-emission electrode,

Figure 1 is a horizontal section of the electrode system in which idenotes the cathode, 2 the control-grld and 3 the screen-grid. Theelectrons issuing from the cathode are drawn to the aux-' anode to 300.The function of the screens 6 is to convey the primary electrons, at thenormal anode voltage, exclusively to the auxiliary cathode. When theanode voltage becomes too high for some reason, for instance only orvolts too high, the paths of the primary electrons are curved so muchstronger that the slower of them find their way directly to the anode.This is represented by dotted lines.

In Figure 2 the arrangement corresponds to that in Figure 1. In thiscase, however, the convex side of the anode 5 faces the auxiliarycathode so that the primary electrons moving in curved paths do noteasily find their way to the anode even with an increased anode voltage.

Figure 3 is a horizontal cross-section of a pushpull tube. The tubecomprises two electrode systems having the auxiliary cathode 4 and theactivated parts i in common. The anode associated with each cathode isdivided into two parts similarly to the secondary-emission electrode 4.It is also possible, however, to design the secondary-emission electrodeand the anode in such a manner that they have circular symmetry normallyto th plane of the drawing, so that they are undivided. In this eventthe cathode and the grids must extend with their axis par allel with theaxis of the secondary-emission electrode. cathode are curved in the samesense as the two opposite anodes. As a result thereof of the distancebetween the said electrodes may be very small so that the auxilarycathode experiences practically no trouble from space charge even whenthe potential difference between them is small. The two anodes 5 areinterconnected through the primary winding 8 of an output transformerhaving a secondary winding 9 tc which the load resistance may beconnected. The anode voltageis supplied to the centre tapping ll] of theprimary winding of the output transformer. A 1

What I claim is: Y I

1. An electron discharge tube comprising means to generate a stream ofprimary electrons directed in a given path, a secondary emissiveelectrode having its active surface positioned in the path of theprimary electrons to intercept said primary electrons whereby secondary"ele'c trons'are emitted therefrom, and an anode electrode having aconvex electron collecting surface spaced from and facing said secondaryemissive electrode, said convex electron collecting surface The sec- Theactivated parts of the auxiliary being positioned outside of saidprimary electron stream path and portions thereof remote from saidprimary electron generating means being spaced closer to said secondaryemissive electrode than portions thereof adjacent said primary electronstream generating means.

2. An electron discharge tube comprising means to generate a stream ofprimary electrons directed in a given patn, a secondary emissiveelectrode having a concave active surface positioned in the path of theprimary electrons to intercept said primary electrons whereby secondaryelectrons are emitted therefrom, and an anode electrode having a convexelectron collecting surface spaced from and facing said secondaryemissive electrode, said convex collecting surface being positionedoutside of said primary electron stream path and portions thereof remotefrom said primary electron generating means being spaced closer to saidsecondary emissive electrode than portions thereof adjacent said primaryelectron stream generating means the spacing between said secondaryemise sive electrode and said anode electrode being unobstructed wherebysecondary emission from said secondary electrode impinges on the saidanode. t i' 3. An electron discharge tube comprising a cathode sourcefor generating a stream of primary electrons directed in a given path, a.sec ondary emissive electrode having a concave active surfacepositioned in the path of the primary electrons to intercept saidprimary elec= trons whereby secondary electrons are emitted therefrom, agrid electrode interposed between the cathodesource and said concaveactive sure face, and an anode electrode having a convex electroncollecting surface spaced from and facing said secondary emissiveelectrode said con vex collecting surface being positioned outside ofsaid primary electron stream'path and portions thereof remote from saidcathode source being spaced closer to said secondary-emissive electrodethan portions thereof adjacent said. primary electron stream generatingmeans the spacing between said secondary emissive electrode and saidanode electrode being unob: stru-cted whereby secondary emission fromsaid secondary electrode impinges on the said anode. ADRIANUS JOHANNESWILHELMUS MARIE vim OVERBEEK,

. REFERENCES CITED The following references are of record in the f le ofthis patent:

UNITED STATES PATENTS Goodall 'Feb. 25, 1947

